Special spinnerets for obtaining yarns of synthetic linear polymers having high regularity of count and of dyability



Dec. 27, 1966 G. BRUNI 3,293,695

SPECIAL SPINNERETS FOR OBTAINING YARNS OF SYNTHETIC LINEAR POLYMERS HAVING HIGH REGULARITY OF COUNT AND OF DYABILITY Filed July 1, 1964 INV EN TOR.

G'deiano 3mm: BY E Afton?- United States Patent 3,293,696 SPECIAL SPINNERETS FOR OBTAINING YARNS OF SYNTHETIC LINEAR POLYMERS HAVING HIGH REGULARITY 0F COUNT AND OF DYA- BILITY Gaetano Bruni, Milan, Italy, assignor to SNIA Viscosa Societa Nazionale Industria Applicazioni Viscosa S.p.A., Milan, Italy, a company of Italy Filed July 1,1964, Ser. No. 379,545 Claims priority, application Italy, July 24, 1963, Patent 702,112 2 Claims. (Cl. 18-8) The present invention relates to a device for spinning of synthetic linear polymers, for instance polyamides, by melt-spinning.

As is known, with such spinning the molten polymer is extruded with the aid of a spinning pump or other suitable device through one or more orifices of a spinneret. With the production of multifilament yarns, spinnerets are employed which have a plurality of orifices each one of which produces a filament or monofilament.

In making such spinnerets the necessity was taken into account that the paths of the individual filaments should not be too different from one another and that the path of the liquid polymer in travelling from the spinning pump towards the orifices should beto the extent possi'bleequal for the various filaments and at any rate should not show such differences as to produce any sensible differences of flow rate between the several orifices.

Ordinarily also spinnerets are used which have their orifices arranged on circles concentric with respect to said spinneret, which ordinarily is circular.

It has been found in industrial practice that multifilament yarns of synthetic linear polymers have count irregularities and differences in their properties of dyability, which characteristics are determining for the quality of the yarn. Said irregularities could not be eliminated completely notwithstanding all the efforts made and the considerable progress realized by the specific technique in the last years.

It has now been surprisingly discoveredand this forms the subject matter of the present inventionthat these irregularities can be completely eliminated by employing spinnerets in which the spinning orifices have a particular arrangement with relationship to the manner in which the cooling of the extruded filaments is carried out, as now will be better specified.

It is known that the extruded filaments are normally cooled by means of a stream of air that is made to flow in a direction transverse to the direction of forward movement of the yarns.

Now according to the present invention, spinnerets are employed wherein the orifices are arranged in a V configuration, the orifices of the spinnerets being arranged with their centres along the sides of the V.

The angle of aperture of the V configuration, namely the angle at of FIGURE 1 formed by the sides of the V, may vary between 30 and 120 and preferably between 45 and 80 and the rectilinear line connecting the sides of the V is preferably not larger than 6 mm. and preferably not smaller than 4 mm.

The two sides of the V may even be replaced by two curve-lined segments having a curvature not excessive. The figure on which the centres of the orifices of the spinneret lie may even be asymmetrical. In any case, the centres of the orifices of the spinneret are arranged in such a manner that the projections of the centres of two adjacent orifices on a plane perpendicular to the direction of flow of the cooling air, should not be smaller than 1 mm. and preferably not larger than 3 mm.

Preferably the shortest path connecting the two in- 3,293,696 Patented Dec. 27, 1966 clined sides of the V configuration, has a length corresponding to the distance between two adjacent orifices of the spinneret, so that on said path there are no orifices not disposed also on the two inclined sides of the V, but on the other hand the invention comprises arrangements in which one or more orifices are disposed on said rectilinear path.

It is surprising that the use of spinnerets ofsuch constitution :brings about elimination of *the irregularities of count and improves the dyeing. properties in the yarns obtained.

Possibly this is because the V configuration permits a stream of cooling air to strike one of the extruded filaments without striking any other filament, so that each filament is invested 'by air that has not previously struck another filament. 'But this does not completely explain the surprising effect due to the invention, since, while this may explain elimination of differences in cooling between one. filament and another, it does not explain how thereby irregularities between adjacent sections of the multifilament yarn, which is formed by the union of all of the individual filaments, are eliminated. Whatsoever the explanation be, the surprising effect of the invention has been experimentally checked and will be more fully made clear by the examples and with reference to the accompanying fignires of which: FIG. 1 represents a bottom plan view of a spinneret made according to one embodiment of the invention, and FIG. 2 shows a spinneret of common type and corresponding in all its dimensions to the-spinneret of FIG. 1 with the sole difference that the holes are disposed uniformly along a circle instead of along a V.

The direction of the How of cooling air is indicated by the parallel arrows.

Example holes of the two spinnerets 5.38 mm. Temperature of the spinning head (measured on the jacket and Dowtherm) 275 C. Speed of the cooling air 0.04 m./1". Temperature of the cooling air 46 C. Speed of collection of the thread 750 m./1.

There were obtained, after successive cold-stretching in the ratio of 1 to 3.6 on a conventional machine, two threads both having the count 40/12.

Said threads collected on a bobbin were checked with the aid of a regularity-meter manufactured by Uster, Zurich, and the following data were found:

Arrangement of the holes of the spinneret Circular V-shape Numberof samples examined 200 200 Average percent irregularity 2. 07 1. 85 Instantaneous absolute maximum irregularity 3. 3. 02

With the yarn obtained from the two kinds of spinneret were manufactured two fabrics on cotton frames.

The two fabrics were dyed with acid dyes and examined as for the-uniformity of dyeing-inthe-direction-"of the warp.

The results were as follows.

Fabric from yarn coming from the spinneret according to FIGURE 2 with the holesarranged on a circle: Slight ma-rks in the warp direction of variable length.

Fabric from yarn coming from thespinneret according to FIGURE 1 with holes arranged in a V: Absolute uniformity of dye;

I claim:

1. ,A spinneret for melt-spinning synthetic linear polymers in a process in which individual substantially parallel filaments are drawnfrom a plurality of spinning orifices of the spinneret in a given spinning direction through a. stream of gaseous cooling medium which impinges on said filaments in a direction essentially transverse to said-spinningdirection, said orifices being arranged in two converging rows which include an angle therebetween, the distance between. any two adjacent orifices .in either of saidr'ows being such that the projections of the centers of these two. orifices to axliue perpendicular to the direction of said stream is at least one millimeter, the rows are so disposed that a line bisecting said angle is parallel to the direction of the stream.

2. A spin-neret for melt-spinning synthetic linear polymers in a process in which individual substantially parallel filaments are drawn from a plurality of spinning orifices of the spinneret in a given spinning direction through a stream of gaseous cooling medium which impinges on said filaments in a direction essentially transverse to said spinning direction, said orifices being arranged in two converging rows which include an angle therebetween, the distance between any two adjacent orifices in either of said rows being such that the projections of the centers of these two orifices to a line perpendicular to the direction of said stream is at least one millimeter, said rows converging to an apex pointing towards the direction in which the said stream impinges on said filaments.

References Cited by the Examiner UNITED STATES PATENTS 2,742,667 4/1956 Clouzeau et al. 188 3,115,385 '12/1963 Beck 18--8 X WILLIAM J. STEPHENSON, Primary Examiner. 

1. A SPINNERET FOR MELT-SPINNING SYNTHETIC LINEAR POLYMERS IN A PROCESS IN WHICH INDIVIDUAL SUBSTANTIALLY PARALRANGED IN TWO CONVERGING ROWS WHICH INCLUDE AN ANGLE LEL FILAMENTS ARE DRAWN FROM A PLURALITY OF SPINNING ORIFICES OF THE SPINNERET IN A GIVEN SPINNING DIRECTION THROUGH A STREAM OF GASEOUS COOLING MEDIUN WHICH IMPINGES ON SAID FILAMENTS IN A DIRECTION ESSENTIALLY TRANSVERSE TO SAID SPINNING DIRECTION, SAID ORIFICES BEING ARTHEREBETWEEN, THE DISTANCE BETWEEN ANY TWO ADJACENT 